An engine of a hybrid vehicle may be started to meet driver demand torque, recharge an electric energy storage device, to warm a passenger cabin, or for other reasons. The engine may be started via an electric machine that supplies torque to the hybrid vehicle's driveline to propel the vehicle. However, engine starting may be noticeable and objectionable to a driver if it results in a driveline torque disturbance. Further, the driver may find engine starting objectionable if the driver recognizes that driver demand torque is not being met while the engine is being started. For these reasons, it may be desirable to provide a way of starting an engine that reduces the possibility of a driver noticing a driveline torque disturbance and reduced driver demand torque response.
The inventors herein have recognized the above-mentioned disadvantages and have developed a driveline method, comprising: estimating a driveline integrated starter/generator torque reserve; supplying a first torque to start an engine in response to the driveline integrated starter/generator torque reserve being less than a threshold; and supplying a second torque, different from the first torque, to start the engine in response to the driveline integrated starter/generator torque reserve being greater than a threshold.
By supplying different torques to start an engine in response to a driveline integrated starter/generator (DISG) torque reserve, it may be possible to provide the technical result of reducing driveline torque disturbances and improving a torque response to a driver demand torque. For example, if vehicle conditions indicate that DISG torque reserve is low, increased DISG torque may be transferred to the engine so that the engine may be started sooner to improve driveline torque response and to assist in meeting driver demand torque. On the other hand, if the DISG torque reserve is high, less DISG torque may be transferred to the engine so that additional DISG torque may be available to meet vehicle operating conditions, thereby reducing driveline torque disturbances.
The present description may provide several advantages. For example, the approach may reduce driveline torque disturbances. Additionally, the approach may provide improve a driveline's response to driver demand torque. Further, the approach may be applied to improve starting of gasoline and diesel engines.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.